SAN FRANCISCO (KRON) — Pieces of glass have fallen off a San Francisco high-rise located at 50 California, KRON4 has learned. The glass pieces fell on the Sacramento Street side of the building.

Sacramento Street and Davis Street are currently blocked off. The San Francisco Fire Department is on the scene. The glass was described as spandrel glass by the building’s owner. Later reports suggested the glass came from a blown-out window.

However, a structural engineer confirmed to KRON4 that the glass that broke was spandrel glass — glass that goes from the actual window down to the floor. Windows breaking in high-rises is very unusual, according to the structural engineer, and having a spandrel glass break is even more unusual.

Clay and California are also closed due to the falling window glass. Winds downtown are extremely intense with people struggling to walk against them. According to a tweet from the San Francisco Fire Department, the window that broke was located on the building’s 21st floor.

“High winds have led to more shards of falling window glass from another building at 50 California,” said Supervisor Aaron Peskin in a tweet. “Problem intersection at Sacramento and Davis means traffic is being diverted.”

“Thanks to emergency responders on the ground triaging situation,” Peskin added.

The fire department called the broken window an “isolated incident” and said there were no injuries. The broken window was most likely weather related, according to SFFD officials.

Last week, glass fell from 555 California Street during high winds. The four blocks surrounding the building were shut down for multiple hours.